Now ....
i recorded 32 Tracks for 2 Hours, played back ... did some Overdubs. All with no Problem, behaves just as on my old Macbook Pro with the MADIFACE directly inserted. I will do some more Liverecordings with a Digico SD8, Soundcraft VI6 and Allen & Heath T112 the next weeks and will report.
I testet it with a RME HDSP MADI Card and also directly hooked on a Studer Vista 5, works fine :-)
The only complaint i have its thats you have to even take more care that you don´t screw up the connections ... the Card sits in the Sonnet Adapter as flabby as it did in my old Macbook Pro, easy to accidentally pushed out, and Thunderbolt also is not a "locking" connection, so take care.
so don´t throw away your old cards ... :-):-):-)